This invention relates to improvements to rock crushers.
In particular, the present invention relates to improvements in rotary) impact rock crushers which provide a greater control over the fracture mechanisms and the grade of rock product.
The many end use applications for rocks require that a range of rock grades are available for use.
The desirable characteristics of a rock product are that it is shaped and graded to suit the duty for which it is required and the strength of the rock is maximized.
The desirable crushing characteristics of a crusher are that there is a high size reduction of the rock, shape and strength of the rock product are maintained or improved and that the crush can be controlled to maximise the desired end product.
There is generally a large compromise between what a crusher will make and what rock product is required. High reduction generally gives poor shape and low strength rock which are undesirable. Low reduction generally gives good shape and high strength which are desirable but high by-product and low output which arm undesirable.
It is common to create a by-product in order to make a specification rock product. This by-product is expensive to produce, has low commercial value and sometimes high environmental costs.
It can be seen that there will be a balance between these characteristics as to which best suits
a) the rock product required; and
b) the crusher making it.
The current problem is that
specifications for rock products are becoming much tighter.
existing crushers lack the control to make a variety of tight specification products at a high rate or without by-product.
Finishing crushers generally fall into the following categories:
Cone Crushers, where rock is crushed by compression between two eccentric metal cones. These machines have good reduction but do not produce fine sand or have good shape.
Hammermills, where rock is crushed by impact with metal hammers attached to a rotor on a horizontal shaft to metal anvil linings in the crusher casing. These machines have high operating costs and the rock product changes rapidly as the crusher wears, i.e. they will not hold the desired rock product specification.
Anvil VSIs, where rock is thrown by a metal impeller (referred to as a rotor) onto metal lining, and is crushed by impact. These machines have good reduction but high operating costs, lower rock strength, bad shape, and won""t hold a desired rock product specification as they wear. Anvil VSIs must also be stopped frequently in order to replace worn anvils, which results in expensive down-time.
Rock on Rook VSIs, where rock is crushed by impact with a rock lined impeller (known as a rotor) on a vertical shaft to rock linings in the crusher casing. These machines have high rock strength good shape and produce good sand but have low reduction, and often produce high by-product (unwanted product).
The main reason for low reduction in the Rock-on-Rock VSI is explained as follows. Rock ejected from the rotor is flung out into the crushing chamber where it strikes the rock bed and circulates in the chamber forming a rock swirl.
Rock on rock crushing occurs when rocks ejected from the rotor impact against rocks in the rock swirl. The greatest impact occurs when there is the greatest possible speed differential between the ejected rocks and the swirling rocks. Generally, the swirl moves rapidly in the same direction as the ejected rock and therefore the motion of the rock swirl particle reduces the impact force between the rock swirl particle and the rock ejected from the rotor.
VSI crushers provide some control over the rate of the rock swirl by variation in speed only (reducing rotor speeds which sacrifices output, and reduction).
Cone and Hammermill crushers only control a specific gap in which rock is crushed which has no control over the rock fracture mechanism.
The Applicant has compiled the following table, subjectively depicting the advantages and disadvantages of each crusher type.
The points given are subjective with the greater number of points, the higher the performance.
Clearly if a crusher could combine the characteristics of one crusher one day to make product xe2x80x98Xxe2x80x99, and be changed in a controlled way to provide the characteristics of a different crusher on another day to make product xe2x80x98Yxe2x80x99 this would be a useful advancement of the art.
It is an object of the present invention to address the foregoing problems of at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.
According to one aspect of the present invention there is provided a rotary impact rock crusher having componentry which includes
a crushing chamber housing, and
a rotor into which rock may be introduced and ejected therefrom positioned in the crushing chamber housing,
the rock crusher characterised in that
the relative angles of at least one of the crusher components is adjustable with respect to the vertical.
In some embodiments, the present invention may be configured so that the rotor angle and the angle of the crushing chamber housing with respect to the vertical are adjustable independently of each other.
In some embodiments, the rotor angle may be varied relative to the crushing chamber without departing from the scope of the present invention.
In preferred embodiments, the present invention may be configured so that the planes of the rotor and the crushing chamber housing are at a fixed relative position to each other so the rotor and crushing chamber housing are moveable together with respect to the vertical
Reference to the componentry angle with resect to the vertical will now be made with reference to the embodiment described in the preceding paragraph, wherein further, the planes of the rotor and the crushing chamber housing arm substantially parallel.
This should not be seen to be limiting in any way, as other arrangements, including those described above may be used according to the present invention without departing from the present invention""s scope.
The rotor componentry will be referred to hereafter as the crushing chamber, which is intended to encompass the crushing chamber housing, and the rotor.
Reference to the angle from the vertical may be made hereafter with reference to xe2x80x9cthe anglexe2x80x9d for convenience.
The adjustable angle may include angles in all directions about the vertical.
Reference to a rotary impact rock crusher may be made with reference to any crusher whereby rock is introduced to the crusher and has velocity imparted to it by means of a centrifugal rotor, which then sects the rock at speed onto a crushing surface which may be a rock, a rock bed, an anvil or a combination of these.
The crushing chamber may further include an anvil configured so that rocks ejected from the rotor impact on the anvil.
The rock crusher may be configured so that the crushing chamber angle is adjusted to control The fracture mechanisms in the crashing chamber,
The rock fracture mechanisms may include shatter/impact, cleavage, attrition, and abrasion (terms defined further).
In some embodiments the control of the fracture mechanisms will be chosen according to the desired rock product output from the crusher.
In all rock crushers, a range of rock grades is always present in the product. A particular fracture mechanism will have a fairly predictable effect on rock and result in a particular rock grade. The choice of fracture mechanisms made by the operator may be made to select and maximise a particular grade of product in the product range.
In some embodiments, the crusher may be configured so that in operation, a rock bed forms on at least a portion of the chamber wall.
In preferred embodiments, the rock bed may form an ever-tightening corner inside a portion of the chamber when the crushing chamber is angled.
The rate at which the ever-tightening corner curves may be controllable by varying the angle of tho rotor, the chamber, or both.
Reference to the ever-tightening corner being formed inside the chamber should be seen to be limiting in any way, as apparatus of the present invention is operable without the ever-tightening corner forming
In preferred embodiments, the crusher may be configured so that where a rock swirl develops in the crushing chamber, the ever-tightening corner inside the chamber has a slowing effect on the rock swirl.
This gives several potential advantages. Rock on rock crushing occurs between rocks ejected from the rotor impacting against rocks in the rock swirl. The greatest rock on rock impact occurs when there is the greatest possible differential between the rocks. Generally, the swirls move in the same direction as the ejected rock and therefore the motion of the rock swirl particle reduces the impact fore between the rock swirl particle and the rock ejected from the rotor.
The slowing of the rock swirl by the ever-tightening corner reduces the swirl speed, thereby increasing the speed differential between the rock swirl particles and the rock ejected from the rotor, which improves the rock on rock crushing effect.
The ability to vary the rate to which the ever-tightening corner curves, means that there is greater control over the fracture mechanisms inside the crushing chamber. This is achieved by being able to vary the angle of the crushing chamber componentry.
It should be appreciated that varying the angle of the rotor or crushing chamber alone may also produce significant commercial advantages as above.
There will potentially be a greater crushing effect with reduced distance between the rotor and the anvil face. Therefore, an operator may vary the crushing phenomena inside the crushing chamber by changing the anvil position within the crushing chamber.
According to a further aspect of the present invention there is provided an anvil segment, configured to be used with an impact crusher which includes a crushing chamber housing and a rotor,
the anvil characterised in that the position of the anvil in the crusher is adjustable.
Preferably, the adjustable position may be the distance between the rotor on the impact crusher and the anvil.
In other embodiments the adjustable position may refer to adjusting the angle, height, pitch, length of the anvil.
According to a further aspect of the present invention there is provided an anvil segment for use with a rotary impact rock crusher, the anvil characterised in that the anvil is configured to have at least one cavity within the anvil structure.
In some embodiments, there may be a plurality of cavities within the anvil structure.
Reference to there being a plurality of cavities within the anvil within the anvil structure should not be seen to be limiting in any way. The anvil may only have one cavity without departing from the scope of the present invention.
The anvil may be configured so that if the anvil surface wears through a cavity behind the wear point will fill with rock emitted from the rotor.
The anvil may continue to wear around the filled cavity until the impact surface on the anvil is regenerated.
While the anvil is wearing down, the filled cavities provided a sufficient impact surface.
Preferably, the cavity positions may be chosen so that when the anvil wears through, the supplementary rock impact surface on the anvil minimises glancing impacts from rock ejected from the rotor.
In preferred embodiments the anvil may be configured so as to be positioned through a wall of the crushing chamber housing.
Further, the anvil may be accessible and/or adjustable from outside the crushing chamber.
This has an advantage in that the operation of the rock crusher may not need to be ceased in order to adjust the anvils.
Further, in the case where many anvils are used as segments forming a complete or partial anvil ring, each segment may be adjusted on its own as required to maintain the desired fracture mechanisms within the crushing chamber, and hence the desired output rock product.
In some embodiments, the cavity may be rectangular.
In other embodiments the cavity may be square, rounded, or may have some other close-curve cross-sectional or plan configuration without departing from the scope of the present invention.
The cavities within the anvil may be configured to have substantially adjacent vertices.
Reference to the cavities having substantially adjacent vertices should not be seen to be limiting in any way.
In some embodiments, the cavities may be spaced apart from each other depending on the application of the anvil.
Preferably, the anvil may be configured so that when the anvil is first in uses the initial impact surface on the anvil has no cavities.
However this should not be seen to be limiting in any way, as in other embodiments it may be desirable to have cavities on the initial anvil crushing surface.
In some embodiment the cavities may have their longest length tuning the direction of the width of the anvil.
In other embodiments the cavities may have their longest length running the direction of the height of the anvil.
In other embodiments the longest length in the cavity may be in the direction of the length of the anvil.
This configuration would be directed towards providing a continuously wearing impact surface as the anvil surface wears, rather than eventuating a regeneration of the anvil impact surface (see further for explanation of regenerative effect).
In some preferred embodiments the anvil way have a stepped impact surface.
In other embodiments, the anvil may have a flat, or curved impact surface
According to a further aspect of the present invention there is provided a plurality of anvil segments as described above.
The plurality of segments may be configured to form a full or partial anvil ring.
The anvil according to the present invention has a number of advantages.
It is usual for the anvil to wear at the points where rock impact occurs, which formerly meant that the entire anvil needed to be replaced once worn through.
The present invention is configured so that if an anvil crushing surface wears through, the cavity will fill with rock. The anvil will further wear until a new flat face is formed. Thus there is an effective regeneration of the flat face(s) making up the crushing surface of the anvil reconstituting the anvil. This is a large cost saving over prior art anvils which must be replaced when the initial impact surface is worn away.
Thus, this prevents or reduces the degree to which the crusher will lose its specification from a worn anvil and the associated unwanted deflections, in terms of the losing control over the desired fracture mechanisms, and the associated rock product.
Further, when an anvil segment is completely worn the anvil segment needs to be replaced, which improves the cost effectiveness of the anvil. An operator can get the benefit of a fill circular anvil ring, but the cost of maintaining only a short anvil segment
The anvil is the most wear-prone component of an anvil crusher, and the expense of maintaining the anvils can mean tat an op ion is not cost-effective. Thus having a longer-lasting anvil, combined with the ability to change each segment individually is of great cost benefit.
Varying the anvil position ray be achieved using a number of means. There may be a sliding mechanism a roller, or some other system allowing the anvil to be moved and held in place.
According to a further aspect of the present invention there is provided a method of controlling the fracture mechanisms in a rotary impact crusher, which includes a crushing chamber housing, and a rotor
characterised by the step of altering the relative angles of the crusher componentry.
According to the above method, there may be included tie further step of adjusting the distance between an anvil in the rotary impact crusher and the outlet of the rotor to achieve the desired fracture mechanism.
Preferably, the method herein before described may be achieved using the crusher previously herein described.
Preferably, the above method may be achieved using an anvil as previously herein described.
The fracture mechanisms referred to previously are now discussed.
Impact/shatter may refer to the degree to which a piece of rock will shatter into different pieces. High impact is usually associated with shatter.
The applicant has found that by increasing the anvil penetration or increasing the angle (which exposes more anvil face) of the crushing chamber, an operator may improve the impact/shatter achievable.
Cleavage is term used to refer to a section of rock parting down a line of weakness within the rock and is normally associated with moderate crushing force.
Cleavage upgrades the strength of the rock product as the resultant particles are generally free from lines of weakness, and thus the deleterious rocks removed.
The applicant has found that the present invention can increase the amount of cleavage by increasing the angle of the crushing chamber, which tightens the curve on the ever-tightening corner, slowing the rock swirl improving rock on rock crushing, and also exposing more anvil face.
Attrition refers to the degree to which a larger rock can be broken down to many smaller parts, usually as a result of a long residence time in the crushing chamber.
The applicant has found that decreasing the angle of the crushing chamber and decreasing anvil penetration increase the attrition effect
Abrasion is a term used to refer to the effect of a particle tumbling at high speed for a long residence time, wearing away at the particle, resulting in a shaping or rounding effect.
The applicant has found that decreasing the angle of the crushing chamber and decreasing anvil penetration increases the abrasion effect.
Changing the rotor speed can also be used to control the fracture mechanisms inside the chamber.
Preferably, the present invention may include an exit means for the rock product.
Preferably the exit means may include a flexible chute.
Reference to the exit means including a flexible chute should not be seen to be limiting in any way, as rigid chutes may also be used without departing from the scope of the present inventions manufacture or use.
In some embodiments, the present invention may be combined with other plant such as devices that sort the grades of rock produced by the crusher, and may also include machinery for packing and transporting the rock produced from the crusher.
Preferably, the chute may be configured so as to vibrate as a result of the operation of the rock crusher to urge the crushed rock down the chute.
Preferably, the chute may be manufactured from a flexible material.
Preferably, the present invention may include a feed tube configured to introduce rock to the crusher.
The change in angle of the crushing chamber componentry forming the ever tightening configuration has a dramatic effect in terms of the control an operator may have over the output of the rock crusher. This is especially noticeable when used in combination with the different crushing effects using the variable distance anvil.
The effect of the ever-tightening corner slows the rock swirl that occurs in rotary impact rock crushers.
The previous discussion in the prior art section outlines how rock on rock crushing occurs between rocks ejected from the rotor impacting against rocks in the rock swirl. The greatest crushing effect occurs when there is the greatest possible speed differential between the rocks. Generally, the swirls move in the same direction as the rock and therefore the motion of the rock swirl particle reduces the impact force between the rock swirl particle and the rock ejected from the rotor.
The slowing of the rock swirl by the ever-tightening circle reduces the swirl speed, thereby increasing the speed differential between the rock swirl particles and the rock ejected from the rotor, which improves the crushing effect.
The ability to vary the rate to which the ever-tightening corner curves, means that there is greater control over the fracture mechanisms inside the crushing chamber. This is achieved by being able to vary the angle of the crushing chamber componentry.
The angling of the present invention also means that the crushing chamber is at a lower position and will have less head room, and can therefore be more easily combined with existing plant. It can be more easily transported with other machinery as well.
It is preferable to have a double belt drive to impart the angular momentum to the rotor.
Normally a xe2x80x9cVxe2x80x9d drive is used with two motors and drive belts positioned substantially opposite each other to drive the rotor.
The present invention enables a xe2x80x9cVxe2x80x9d drive arrangement to be employed whereby the motors and belts are positioned at an acute angle relative to each other to drive the rotor.
The motors can be positioned on the side opposite the side where the rock is ejected from the rock crusher.
This makes the present invention more compatible with supplementary machinery.
The advantages of the present invention result in a device that has a significantly higher control over the fracture mechanisms occurring in the rock crusher, than was previously achievable in the prior art crushers. An operator may choose a particular rock product output one day, and then adjust the settings on the crusher the next time to maximise another grade of rock in the rock product.
The present invention enables the operator to change the settings to dial up a particular rock product.
The present invention also allows the operator to adjust the settings on the rock crusher while it is operating in order to maintain the rock product specification at optimum levels at all times.